The present invention relates generally to ironing machines and more specifically to an improved cupper sleeve support for a drawing and ironing machine.
In the formation of a "two-piece" container, it has been customary to utilize a plurality of die assemblies that cooperate with a punch for converting circular metal discs into finished containers which have a sidewall and an integral end wall. One of these processes consists of originally drawing a circular metal disc into a cup utilizing what is commonly referred to as a cupping machine. The cup is then transferred to a bodymaker wherein the cup is converted into the finished container. In one process, which is being used commercially, the preformed cup is first redrawn to a smaller diameter and larger height and then is substantially simultaneously converted to an ironed container wherein the sidewall thickness is reduced in one or more steps. One type of such commercial machine is produced by Ragsdale Bros., Inc. and is identified as a Model CR-24 canwall drawing and ironing press. Normally the material for such containers is either aluminum or tinplate.
In such a process, a punch normally cooperates with a plurality of ironing dies and the stroke of the punch is fairly long in order to produce conventional 12 and 16 ounce containers. The length of the stroke of the punch for the bodymaker or press has heretofore created substantial problems in producing a satisfactory container which has a uniform wall thickness in the sidewall thereof. One of the problems encountered has been in maintaining all of the elements in very accurate alignment with respect to each other in order to produce a finished container which has a uniform wall thickness around the entire perimeter thereof and also the entire length thereof.
In order to alleviate some of the problems in maintaining accurate alignment between the various dies and the punch, several proposals for producing floating ironing dies have been proposed. For example, British Pat. No. 724,251 published Feb. 16, 1955 discloses a method of supporting ironing dies that will accommodate movement of the dies with respect to the punch but will also provide a self-centering feature which theoretically will reposition the die to a predetermined position whenever all external forces have been removed. The particular arrangement for accomplishing the self-centering and floating feature in the assembly disclosed in the British patent consists of cooperating inclined surfaces between the ironing die and its support mechanism with a biasing mechanism which will automatically center the ironing dies with respect to a predetermined axis whenever external forces are removed. The biasing mechanism in this patent has been illustrated as either consisting of an elastomeric member or rubber ring which produces a centering action between an ironing die and a cooperating support. Alternatively, the centering means in the disclosed patent also shows the use of springs that cooperate with the ironing die and the support to center the ironing die with respect to a predetermined axis.
One additional problem that has been encountered in the formation of two-piece drawn and ironed containers has been encountered when the cup is initially formed and then is redrawn just prior to the ironing of the sidewall. In a redraw operation just prior to the ironing of the sidewalls of the cups, it is customary to hold the cup through what may be termed a cup holder sleeve in an accurate position with respect to the redraw ring just prior to the punch entering into the cup and forcing the cup through the redraw ring. It has been found that, under certain conditions, the cup holder sleeve is not accurately centered, while applying uniform hold-down pressure on the cup to hold the cup in a fixed position with respect to the redraw ring. This will produce an uneven redrawn cup which can produce a tear-off of the longer end either in the redraw stage or in subsequent ironing stages.
It has also been found that when there is no accurate alignment between the punch and the redraw which reshapes the cup, the wall thickness of selected portions of the cup may be reduced during the redraw process which results in ultimately having varying thicknesses in different portions of the sidewall of the finished container.
It has also been determined that if the cup holder sleeve face does not apply a uniform pressure to the cup it may wrinkle in selected areas during the redraw application.